This detection rule is designed to identify potential brand spoofing attacks specifically targeting the Dropbox file-sharing service. The rule checks for inbound emails where the sender's domain is spoofed to appear as if it originates from 'dropbox.com'. Key elements evaluated by the rule include the DMARC (Domain-based Message Authentication, Reporting & Conformance) authentication status of the email. If the email fails DMARC validation, it may indicate an impersonation attempt. Additionally, the rule also verifies that the message-ID does not end with '.dropbox.com', which further mitigates false positives stemming from legitimate emails due to misconfigurations. This rule addresses common attack types such as Credential Phishing and Malware/Ransomware delivery methods, and employs techniques characterized as Impersonation (Brand) and Spoofing. Detection methods primarily involve analyzing email headers and sender information to determine authenticity.